The present invention relates in general to equipment and methods for conveying pulverized material, and in particular to a new and useful blow bottle assembly and method for continuously transporting fine solids in dense phase in intrafurnace (into a furnace) sorbent injection applications.
Continuous flow, high pressure feed systems contain either two pressure blow bottles in parallel or three lock hoppers in series. These systems have a relatively high ratio of solids to actual unit volume of gas and are often referred to as "dense phase" systems. These systems operate on the principle of converting static pressure to velocity pressure via sequencing batch processes. On lower pressure systems, where the ratio of solids to gas volume is relatively low (possibly one tenth or less of that in a dense phase system) a rotary feeder can be used provide a continuous flow by dropping sorbent into a horizontal process pipe. Rotary feeders are generally not used in dense phase transport because of pressure limitations.
The Babcock & Wilcox Company has used continuous blow bottles as part of a pulverized fuel delivery system for several years. This system is known as the PCI (pulverized coal injection) system and is disclosed for example, in U.S. Pat. Nos. 3,689,045 and 3,720,351.
U.S. Pat. No. 4,668,130 also discloses a dense phase coal feeding system wherein carbonaceous solids such as coal and oil shale are fed to a high temperature processing vessel without bridging and plugging problems that would interrupt the flow of the solids into the processing vessel. The solids are passed at a controlled rate from a feed vessel into a first conduit communicating with the feed vessel. The solids are then passed through the first conduit into a second conduit which communicates with the first conduit and the processing vessel, and the second conduit contains a scraper for scraping the inside walls of the conduit. The pressure in the feed vessel is maintained at a level higher than that in the processing vessel by passing a sufficient amount of a gas into the feed vessel such that the solids are passed through the second conduit into the processing vessel in dense phase pneumatic flow as the scraper scrapes the inside walls of the second conduit, thereby preventing any bridging or plugging. Normally, the scraper will consist of a wire helix which is rotated inside the second conduit.
U.S. Pat. No. 4,397,657 teaches an apparatus for feeding a continuous supply of carbonaceous material into a pressurized reactor. A first rotary gas lock is provided for receiving the material from ambient atmospheric conditions. The first rotary gas lock is supplied with a flow of nitrogen as a sealing gas to prevent air from entering the lock and the apparatus. The first lock transfers the material to a second rotary gas lock which in turn transfers the material to a screw conveyor for delivery to the interior of the reactor. The second lock is supplied with a flow of a clean product gas as a buffer gas. The clean product gas supplied to the second lock is at a pressure greater than the pressure in the reactor and prevents flow of gases from the reactor to the apparatus. Thus a continuous feed is provided.
U.S. Pat. No. 4,244,705 discloses a triple rotary gas lock arrangement for providing a continuous feed to a kiln.
U.S. Pat. No. 3,775,071 relates to an apparatus for feeding dry coal to a region of superatmospheric pressure (such as a coal gasifier or coal liquefaction reactor) wherein three pressure hoppers are used; one for low pressure, one for intermediate pressure and one for high pressure.
U.S. Pat. No. 3,729,105 relates to liquid sealed solids lock hoppers and, as stated in the specification, the process may be made continuous by providing two or more lock hoppers for use in tandem.
U.S. Pat. No. 4,247,240 discloses a feed arrangement quite similar to U.S. Pat. No. 3,729,105 discussed earlier.
U.S. Pat. No. 3,556,606 discloses a system for particulate transfer. According to this process, there is provided a method for obtaining uniform flow of particulate matter from a supply source through a flow control means positioned on the outlet thereof, which comprises: sensing the pressure within the supply source on the upstream side of the flow control means; establishing flow in a conduit in by-pass relationship to the flow control means in response thereto from the upstream side of the flow control means to relieve gaseous obstruction to flow; and establishing flow of the particulate matter from the supply source through the flow control means.
None of these patents suggest means for measuring the weight of a single continuous feed flow bottle and means for controlling the process air or gas supplied to the bottle to maintain a continuous dense phase flow from the bottle by keeping the level of solids therein within a given range.